When ferromagnet (FM) and antiferromagnet (AFM) are coupled, exchange bias can be generated at the interface of FM and AFM which acts as a bias field in the hysteresis loop.
I am particularly interested in the case that FM has perpendicular magnetic anisotropy (PMA) and the localized magnetization in AFM lies in the plane. In this case, it is possible to generate an in-plane bias field to the FM layer.
In a system like PtMn + Co/Ni multilayer, where the Curie (Neel) temperature TC (TN) are both very high ( > 300 C), a typical way to induce this in-plane bias field is by applying a large in-plane field (~ 1T) and annealing the sample at ~300 C, which is below TC. I assume that the annealing is required because it is not a good idea to heat the sample above TC and therefore change the property of the material.
Now, my question is: If I have a similar system (FM with PMA, in-plane AFM), but with room temperature > TC >TN, can I induce an in-plane field by applying a large in-plane filed above TN and then cool the sample to a temperature below TN?
Relevant paper:
Annealing to get bias field:
https://www.nature.com/articles/nmat4566?cacheBust=1509880778548
Neel temperature of AFMs:
Article Temperature dependence of the exchange-bias field of ferroma...
To answer your question: you could try , in principle it would work, but I would bet money that it would destroy your layer structure. In which case:
So you want to set your AFM in-plane?
If so just do your anneal with a sufficiently high field to pull the FM magnetisation orientation in-plane. If you use a thermal activation process to set the AFM (see: https://doi.org/10.1016/j.jmmm.2009.12.011 ) a temperature of 250-300C for 90mins should be sufficient.
Too high of a temperature and you risk diffusion of your system destroying your desired properties. For example, Mn diffusion in IrMn occurs at a (significantly) damaging rate above 350C.
Another tip - choose your AFM seed layer carefully. This will control the grain orientation of your AFM which will of course dictate the magnetocrystalline anisotropy axes.
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